package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CashClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CashClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    /**
     * @param key
     * @param value
     * @param time
     * @param unit
     */
    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    /**
     * 逻辑过期
     *
     * @param key
     * @param value
     * @param time
     * @param unit
     */
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {

        //设置逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    /**
     * 缓存穿透
     *
     * @param keyPrefix
     * @param id
     * @param type
     * @param dbFallback
     * @param time
     * @param unit
     * @return
     * @param <R>
     * @param <ID>
     */
    public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在直接返回;
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值
        if (json != null) {
            //4.存在，但是是一个空值，直接返回错误信息
            return null;
        }
        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if (r == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(r), CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6.存在，写入redis在返回
        this.set(key, r, time, unit);
        //7.返回结果
        return r;
    }
    /**
     * 缓存重建的线程池
     */
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    /**
     * 逻辑过期解决缓存击穿
     * @param id
     * @return
     */
    public <R,ID> R queryWithLogicalExpire(ID id,String keyPrefix,Class<R> type,Function<ID, R> dbFallback,Long time,TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)) {
            //2.1存在，返回
            return null;
        }
        //3.命中需要判断过期时间，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //4.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //4.1未过期，直接返回店铺信息
            return r;
        }
        //4.2已过期，需要缓存重建
        //5缓冲重建
        //5.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean islock = tryLock(lockKey);
        //5.2判断是否获取锁成功
        if (islock) {
            //5.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                //重建缓存
                try {
                    //先查数据库
                    R r1 = dbFallback.apply(id);
                    //再写入redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                    //TODO 再次检测缓存是否过期
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //5.4返回过期的商品信息
        return r;
    }

    /**
     * 获取锁
     * @param key
     * @return
     */
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    /**
     * 释放锁
     * @param key
     */
    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }
}
